1. Field of the Invention
Aspects of the present invention relate to a method and apparatus for supporting the mobility of a mobile node under a mobile Internet protocol version 6 (MIPv6) environment, especially under a hierarchical MIPv6 (HMIPv6) environment.
2. Description of the Related Art
As wireless communication has been in great demand in recent years, various new wireless Internet networks, as well as existing mobile networks and wireless LANs, appear in succession. In particular, improvements in the performance of mobile terminals, such as portable phones, personal digital assistants (PDAs), laptop computers, etc., and technological development of wireless communication allow users to expect the same high-quality Internet service in a wireless environment that they have so far experienced in a wired environment with desktop computers.
Meanwhile, in order to use existing Internet services, the mobility of mobile terminals should be supported in Internet protocol (IP) based Internet networks. In particular, mobility should be supported not only in physical and link layers, but also in IP layers. With this background, a representative protocol, MIPv6, has been developed.
FIG. 1 shows a configuration of a conventional MIPv6. Referring to FIG. 1, the conventional MIPv6 environment comprises a mobile node (MN) 11, a home agent (HA) 12, a foreign agent (FA) 13, and a correspondent node (CN) 14.
The mobile node 11 moves from a home network managed by the home agent 12 into a subnet managed by the foreign agent 13, at which time the mobile node 11 generates a Care of Address (CoA), which is an IP address, to be used in the subnet. The mobile node 11 sends a Binding Update (BU) message to the home agent 12 to inform it of the CoA, and it in turn receives a Binding Acknowledgement (BA) message from the home agent 12. Through such a binding process, the mobile node 11 can maintain connectivity with the home agent 12 or the correspondent node 14. When the correspondent node 14 sends data to a previous address of the mobile node 11, the home agent 12 snatches the data and transfer it to the present address of the mobile node 11 located in the subnet managed by the foreign agent 13.
However, if the mobile node 11 is at a far distance from the home agent 12, it takes a long time to perform the binding process, and thus the mobile node 11 is likely to lose its connectivity with the correspondent node 14, resulting in data loss and transmission delay. To solve this problem, a method of localized mobility management has been suggested. According to the method, a shift of the mobile node 11 into a new subnet will avoid influencing, as much as possible, the binding of the mobile node 11 with the home agent 12 or the correspondent node 14.
An exemplary scheme known to those skilled in the art to implement the method of localized mobility management is hierarchically configured MIPv6 (HMIPv6). Under the HMIPv6, every predefined area having a plurality of subnets sets up a mobile anchor point (MAP), a local agent that is representative of a mobile node in the predefined area. The MAP is in charge of the mobility of the mobile node in the predefined area, so as to hide the mobility of the mobile node from a home agent or a correspondent node.
FIG. 2 shows the configuration of a conventional HMIPv6. Referring to FIG. 2, the conventional HMIPv6 environment comprises a mobile node 21, access routers (ARs) 22 and 23, a mobile anchor point (MAP) 24, a home agent 25, and a correspondent node 26.
The mobile node 21 moves from a subnet managed by the access router 23 to another subnet managed by the access router 22. At this time, the mobile node 21 obtains information regarding the MAP 24 from a router advertisement message from the access router 22 that manages the subnet where the mobile node 21 is now located. The mobile node 21 performs a binding process with the MAP 24 by using a Local CoA (LCoA) generated by the mobile node 21 and a Regional CoA (RCoA) included in the information regarding the MAP 24. RCoA is an IP address of the MAP 24, but is recognized as an IP address of the mobile node 21 by the home agent 25 or the correspondent node 26. Therefore, as long as the mobile node 21 moves between subnets within an area covered by the MAP 24, the mobile node 21 needs only to perform the binding process with the MAP 24. Thus, it can hide its mobility from the home agent 25 or the correspondent node 26, thereby reducing binding procedures with the home agent 25, as defined in MIPv6 and reducing the handover time.
However, in the case where the access router 22 of a subnet into which the mobile node 21 has just moved does not support HMIPv6-based functions, that is, the access router 22 does not include MAP options, the mobile node 21 cannot obtain information regarding the MAP 24 and the connection between the mobile node 21 and the home agent 25 is terminated. Since not all access routers of all networks guarantee to support HMIPv6-based functions, measures for solving the problem in this case are needed.